Poland's Foreign Minister Stefan Meller has announced his resignation as a populist Euro-sceptic party is poised to enter the ruling coalition.
Stefan Meller was previously a top ambassador
Mr Meller, 63, had threatened to leave the government if Prime Minister Kazimierz Marcinkiewicz agreed a deal with the agrarian Self-Defence party.
Its leader, Andrzej Lepper, has a reputation for direct action campaigns, such as blocking roads.
The conservative coalition led by Law and Justice was finalised on Thursday.
The deal boosts the party's support but still denies it a working majority.
Law and Justice has struggled to form a coalition since its narrow win in parliamentary polls in September.
Mr Lepper is expected to be nominated for the post of deputy prime minister.
The coalition also includes members of the right-wing nationalist Polish Families' League.
According to the BBC's Adam Easton in Warsaw, the government's alliance with Eurosceptic and nationalist parties had provoked concern in Brussels that Poland would become a less reliable partner in the EU.
A spokesman for the Polish foreign ministry said the minister had handed in his resignation to the head of government.
"He gave as the motive for his decision the creation of the new coalition," spokesman Pawel Dobrowolski said.
"He will continue to manage current affairs until the nomination of the new minister."